The oven disclosed herein relates to devices of the type disclosed in U.S. Pat. No. 4,154,861, entitled "Heat Treatment of Food Products"; U.S. Pat. No. 4,338,911, entitled "Cooking Apparatus"; U.S. Pat. No. 4,377,109, entitled "Apparatus for Baking Food Products Such as Pizzas"; U.S. Pat. No. 4,479,776, entitled "Thermal Treatment of Food Products"; U.S. Pat. No. 4,679,542 entitled "Fan-Plenum Configuration"; U.S. Pat. No. 4,462,383, entitled "Impingement Food Preparation Apparatus"; U.S. Pat. No. 4,474,498, entitled "Multiple-Pass Impingement Heating and Cooling Device"; and U.S. Pat. No. 4,757,800 entitled "Air Flow System for A Low Profile Impingement Oven."
Ovens of the type disclosed in Smith U.S. Pat. No. 4,679,542 have enjoyed substantial commercial success for food service applications and particularly in fast food operations such as cooking pizza and other food products in restaurants and food service establishments. Food products are rapidly heated by air streams which impinge against the surface of food products moved through the oven on a conveyor.
Convection ovens employ high volumes of rapidly moving air which in some configurations tend to draw cool outside air through entrance and exit openings through which a conveyor extends and to permit the escape of heated air through the conveyor openings. Circulation of air into and out of the oven wastes energy required for heating the rapidly circulating air and increases the warmup time required to place the oven into service. Further, the escaping hot air may cause discomfort of nearby persons.
The enhanced efficiency and rapid heating of food products in impingement ovens is dependent upon delivering defined air streams to impinge upon discrete areas of a moving food product. Blowers have been positioned either adjacent one side of the conveyorized oven or above or below the conveyor for circulating air. However, the suction toward the inlet of one side of the conveyor has caused air to be drawn into the sides of the inlet and exit openings nearest the blower and-exhausted through sides of the inlet and exit openings on the opposite side of the conveyor.
The conveyorized convection ovens described in the above identified patents use air ducts extending across the width of the conveyors to supply the air streams. Uniformity of the effective heat transfer across the width of the conveyor is very important for reproducible operation and uniform baking. Inspiration of outside air causes localized temperature differences; and, uneven intensity of an application across the width of the conveyor causes uneven baking.